Fire officials watch the growing smoke from a brush fire that started on Camp Pendleton when a Marine helicopter crashed Monday in De Luz, Calif. (AP Photo/Lenny Ignelzi)

CAMP PENDLETON, Calif. >> A helicopter that went down during a training exercise at Southern California's Camp Pendleton killed two Marines and set off a fast-moving brush fire on the base today.

Base firefighters were battling the blaze, which had spread to 50 acres three hours after the 1 p.m. accident.

The wreck involved a twin-engine, two-seat AH-1W Cobra attack helicopter belonging to the 3rd Marine Aircraft Wing, a Marine Corps statement said. It crashed in the southeast corner of the base near the community of Fallbrook, and the fire was moving near the base's border with the town of De Luz, the Marine Corps statement said.

The base's firefighters were using air tankers to fight the fire.

The Marines died at the scene. Their names won't be released until their families have been notified, officials said.

Several accidents have happened in recent months involving Marine Corps training in Southern California, including a fatal accident in July.

In August, two Marines were ejected from their F/A-18 Hornet fighter jet as it plunged toward the Pacific Ocean. The two Marines spent four hours in the dark, chilly ocean before they were rescued. Both suffered broken bones and are undergoing rehabilitation at a San Diego hospital.

In July, a decorated Marine from western New York was killed during a training exercise when his UH-1Y helicopter went down in a remote section of Camp Pendleton, north of San Diego.

Another Hornet sustained at least $1 million damage when its engine caught fire on March 30 aboard the USS John C. Stennis during a training exercise about 100 miles off the San Diego coast. Eight sailors, a Marine and two civilians were injured.

The Navy has said debris in the engine is the suspected cause of that fire.